Closed-form solution to thin-walled box girders considering effects of shear deformation and shear lag

Considering three longitudinal displacement functions and uniform axial displacement functions for shear lag effect and uniform axial deformation of thin-walled box girder with varying depths,a simple and efficient method with high precision to analyze the shear lag effect of thin-walled box girders was proposed.The governing differential equations and boundary conditions of the box girder under lateral loading were derived based on the energy-variational method,and closed-form solutions to stress and deflection corresponding to lateral loading were obtained.Analysis and calculations were carried out with respect to a trapezoidal box girder under concentrated loading or uniform loading and a rectangular box girder under concentrated loading.The analytical results were compared with numerical solutions derived according to the high order finite strip element method and the experimental results.The investigation shows that the closed-form solution is in good agreement with the numerical solutions derived according to the high order finite strip method and the experimental results,and has good stability.Because of the shear lag effect,the stress in cross-section centroid is no longer zero,thus it is not reasonable enough to assume that the strain in cross-section centroid is zero without considering uniform axial deformation.

Improved concept models for straight thin-walled columns with box cross section

This paper focuses on developing improved concept models for straight thin-walled box sectional columns which can better predict the peak crushing force that occurs during crashworthiness analyses. We develop a nonlinear translational spring based on previous research and apply such a spring element to build the enhanced concept models. The work presented in this article is developed on the basis of the publication of the author (Liu and Day, 2006b) and has been applied in a crashworthiness design issue, which is presented by the author in another paper (Liu, 2008).

Lateral static and dynamic characteristics of thin-walled box girder

To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions： w （x） , U（x） and O（x） are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach.

Factors Affecting Box Office during Broad Spring Festival Based on Partial Least Squares Regression

The box office during the later Spring Festival shows an attractive prospect.This paper studied the factors affecting total box office during the broad Spring Festival which is from the Spring Festival to the Lantern Festival.Data of films released during the broad Spring Festival from the years 2016 to 2019 in China were gathered,and the impact of eight explanatory variables on the box office during the broad Spring Festival was empirically analyzed by partial least squares(PLS)regression with software SIMCA.The results suggest that word-of-mouth has the most positive effect on the box office during the broad Spring Festival.Later propaganda has a positive effect,while early promotion has a negative effect on the box office.Director’s influence has a positive effect,while actor’s influence does not contribute much to the box office.Length of the trailer has a negative effect.The film format of 2D or 3D doesn’t contribute much to the box office.

WRINKLE LIMIT BLANK HOLDER FORCE MODELS IN SQUARE-BOX DEEP DRAWING WITH VARIABLE SEGMENT BLANK-HOLDERS

Constituting the reasonable control models of the wrinkle limit blank holder forces is the sticking point of the processes of the deep drawing with variable blank-holder forces, especially in the square-box forming. To begin with, a mode of segmenting flange of the square-box into eight zones is put forward according to the fact that the uniformity of flange deforming can be improved by control-ling segment blank-holders. Considering the integral influence of shear stress, a new concept, strain relaxation factor is defined. Hereby, the law of distribution of stress and stain in the deforming flange of square-box is achieved. Then based on these mechanical analysis models and the energy principle, the wrinkling flexivity functions of the straight flange and the circle flange are given, and the corresponding formulae of wrinkling limit blank-holder force in these two situations are also educed. In these processes, ply-anisotropy, strain hardening, thickness and friction are considered. In the end, a calculating example is designed to validate the rationality of the formulae of wrinkling limit blank-holder force, at the same time, the influences of the ply-anisotropy exponent and the strain hardening exponent on the wrinkle limit blank holder forces are also analyzed.

A comparative study on the hull strength of a ship with thin-walled box girders

Based on the Finite Element Analysis and Thin Walled-Box girder Mechanics, two design concepts of adding box girders under main deck in order to increase the hull strength of ship are presented. By comparison and analysis on the longitudinal strength, torsion strength and deck buckling between designed concepts and the original concept, it is found that by adding box girders under the main deck, the weight of hull structure is increased by lower than 10%, but the stress on the plate of the main deck is reduced by about 10%, the stress on the plating of the second deck is reduced about 20%. The shear stress on the plating of both of the main deck and second deck is reduced, but the shear stresses in several nodes are increased. Also the capability of resisting damage to ship is obviously increased by adding box girders under the main deck. The deck buckling is also increased by more than 90%. Consequently, the box girders added under the main deck are useful and effective to increase the strength of hull and ship survivability.

Powell's optimal identification of material constants of thin-walled box girders based on Fibonacci series search method

A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell＇s optimization theory is used to perform the stochastic identification of material constants of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell＇s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element （FCSE） method. Some classical examples show that Powell＇s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell＇s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses axe simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.

THE APPROXIMATE ANALYTICAL SOLUTION FOR THE BUCKLING LOADS OF A THIN-WALLED BOX COLUMN WITH VARIABLE CROSS-SECTION

For a thin-walled box column with variable cross-section, the three governing equations for torsional-flexural buckling are ordinary differential equations of the second or fourth order with variable coefficients, so it is very difficult to solve them by means of an analytic method. In this paper, polynomials are used to approximate the geometric properties of cross-section and certain coefficients of the differential equations. Based on the energy principle and the Galerkin's method, the approximate formulas for calculating the flexural and torsional buckling loads of this kind of columns are developed respectively, and numerical examples are used to verify the correctness of the solutions obtained. The results calculated in this paper provide the basis for demonstrating the stability of thin-walled box columns with variable cross-section. This paper is of practical value.

Box-Jenkins模型偏差补偿方法与其他辨识方法的比较

对于存在相关噪声干扰的Box—Jenkins系统,本文借助于偏差补偿原理,推导了一个偏差补偿最小二乘(BCLS)辨识方法;理论分析说明BCLS方法能够给出系统模型参数的无偏估计,并将提出的方法与递推增广最小二乘算法和递推广义增广最小二乘算法进行了比较研究;用仿真试验分析了这些算法的各自特点和适用范围。

扎染工艺下铜鼓纹样方巾盲盒设计

针对当今盲盒设计形式乏味单一等问题,文章基于扎染工艺,将广西铜鼓纹样融合在盲盒设计中,先分别从文化价值和美学价值两个方面具体分析铜鼓纹样在方巾盲盒设计中的应用价值,然后通过对铜鼓纹样提取、解构及重组的方式对铜鼓纹样方巾进行多样化图案设计,最终采用扎染工艺进行铜鼓方巾的盲盒设计,以增强盲盒设计的民族性和多样性,为盲盒设计注入新的生命力。

基于变分模态分解和SG滤波的二次谐波降噪

针对可调谐半导体激光器吸收光谱学,在测量低浓度气体过程中二次谐波存在的噪声问题,提出利用变分模态分解(VMD)和Savitzky-Golay滤波(SG滤波)相结合方法(简记为VMD-SG滤波)对含噪信号进行降噪。分析了VMD平衡参数的最优选取,利用所设框长调节因子P,选取SG滤波的最优框长。通过与其他几种降噪算法相比,VMD-SG滤波降噪算法在信噪比、均方根误差、波形恢复、二次谐波特征点误差方面均表现较优。在信噪比(SNR)为-7.8389 dB下该算法SNR提升量为22.047 dB,均方根误差为0.0154,与标准二次谐波相关系数为0.985。结果表明,基于VMD-SG滤波降噪算法的可调谐二极管吸收光谱复合降噪技术,在弱信号方面可以提高信号质量,有利于提高气体反演精度、系统检测灵敏度。

RobotStudio的方形锂电池搬运装盒仿真研究

为解决体积较小的锂电池如柱状类18650锂电池、方形锂电池和纽扣状锂电池等装盒包装工作导致的占用生产线劳动力,以及繁琐重复的小体积锂电池手工装盒易导致工厂劳动人员疲劳等问题,以方形锂电池搬运装盒为研究对象,设计出一种用搬运机器人取代人工操作的方案,利用RobotStudio软件模拟这一过程。最后利用RobotStudio分析搬运机器人速度对其功耗的影响,为实际生产提供参考依据。

新型高填方桥台设计研究

在台后填方高度超过10 m且台前无法放坡的高填方地形路段,桥台需要能抵抗台后较大的土压力,具有较大的竖向承载力和水平承载力且能克服台后填土较大的不均匀沉降,而传统桥台类型难以满足上述需求。为此,以某台后填方为10.6 m的跨站前广场桥为例,提出在台身后设置箱室,并在纵桥向采用3排桩基的箱型桥台方案;同时根据桥梁总体布置,对该新型高填方桥台进行了构造设计并采用有限元软件计算验证该桥台结构的可行性。结果表明:新型高填方桥台各力学性能指标均满足规范要求,能够适用于台后高填方的地形,台前无需放坡即可保证桥下站前广场的通行空间。

红外光谱结合统计学方法对纸质包装盒的检验研究

目的建立一种高效准确的红外光谱检验纸质包装盒的研究方法。方法利用傅里叶变换红外光谱仪测得了56个不同类型不同来源的纸质包装盒的红外光谱数据;根据纸盒主要填料的不同,将样品初步分为三大类;利用主成分分析对初步分类后的数据降维,提取出4个主成分,再利用系统聚类将样品最终分为6组,使用K-means聚类算法结合Pearson卡方检验进行验证,与最终分类的结果基本吻合。基于该分组,训练朴素贝叶斯分类、随机森林模型、XGBoost分类3种判别模型,实现对新样品组别的分类预测。结果56个快递包装纸盒样品被分为3类,而后进一步细分为6组,3种判别预测模型均有较高的准确率,其中随机森林模型的准确率最高。结论该方法快速方便地实现了对样品的区分,并且可以实现无损检验,为犯罪现场纸质包装盒的鉴别提供依据,从而为公安侦查工作的开展提供帮助。

多源信息融合技术在方形箱体焊接质量检测中的应用

方形箱体结构复杂、焊缝数量多、缺陷类型多样,给传统的焊接质量检测方法带来了挑战,为此必须研发先进的检测技术和分析技术。多源信息融合技术依靠其全面性、准确性、智能化等优势,在焊接质量检测中展现出广阔的应用潜力。文章阐述多源信息融合技术在方形箱体焊接质量检测中的应用,旨在为相关研究者提供参考。

Shear deformable finite beam elements for composite box beams

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

基于奇异值分解的Box-Jenkins模型参数估计算法

基于奇异值分解和递推广义增广最小二乘原理,提出了Box-Jenkins模型参数估计的一种递推算法.常规的递推广义增广最小二乘算法对舍入误差较为敏感,会导致协方差矩阵失去正定性和对称性,产生病态条件问题,引起数值不稳定现象.为了改善参数估计的性能,利用协方差矩阵的奇异值分解技术,推导出Box-Jenkins模型估计算法.该算法辨识精度高,收敛速度快,数值稳定性好.仿真表明,随着噪信比的增大,新算法仍然具有良好的性能.

基于Box-Cox变换的水位流量关系拟合

在水位流量关系曲线拟合中,非线性最小二乘法(Non-linear Least Square,NLS)是广泛运用的方法。但NLS中采用的对数变换有时不能起到稳定方差的作用,且没有考虑异方差会导致水位流量关系中的参数和流量估计值不可靠的问题。为了克服这个局限性,采用Box-Cox变换进行改进,并利用极大似然估计法(MaximumLikelihood Estimation,MLE)对变换后的模型进行参数估计。结果表明:相比于NLS中的对数变换模型,基于Box-Cox变换模型能更好地得到稳定方差,更倾向产生正态分布。并且发现对数变换模型是Box-Cox变换模型的一个特例,因此Box-Cox变换模型能够更合理地推断水位流量关系,在实际应用中的适用范围更广。

一种板球系统的Box-Jenkins模型辨识研究

板球系统是一种典型的非线性多变量系统,是先进控制理论、系统辨识和状态估计等方法的典型验证平台,其主要功能是让小球在平板上按照期望的轨迹运行。由于机器老化,先前的机理模型已不能表示板球系统的动态特性。为保证控制精度,为板球系统后期先进控制器的设计提供模型依据,本文将已有的关于离散系统的BoxJenkins模型辨识技术,推广应用到连续时间板球系统的模型中,利用参考输入信号的方法设计出持续激励作为输入信号,采用辅助变量法和最小二乘法来分别辨识板球系统模型和噪声模型,利用双线性变换得出板球系统的连续时间Box-Jenkins模型,通过数值仿真实例,验证了这种方法的有效性。

低成本T-box多信息融合导航算法

车载远程设备T-box具有车辆远程诊断及监控等功能,低成本方案的T-box定位接收模块精度低,易受城市中高楼、高架等建筑影响,出现定位点丢失或高噪声定位点。为解决低成本T-box易出现的定位问题,提出了一种通过去除经纬度高噪声数据点以及多数据融合提高导航精度的方法。T-box带有微型惯性测量单元模块和车载诊断系统模块,分别采集微型惯性测量单元数据和汽车速度;最小二乘法拟合汽车行驶的轨迹去除原始定位数据中高噪声经纬度数据点;最后与汽车速度、惯性数据进行扩展卡尔曼滤波融合得到新的经纬度数据,与高精度定位数据对比,该方法能有效提高车载远程设备定位精度。